The invention relates to a display device comprising an evacuated envelope having a flat display window which is provided with a luminescing phosphor screen, which envelope accommodates a tensed linear thermionic wire cathode for emitting electron and a first electrode having a slit for passing electrons, so that electron beams are formed.
Such a display device is known from U. S. Pat. No. 4,451,758, in which a number of parallel disposed wire cathodes are accommodated in the envelope. A general problem is such a display device is the sensitivity of each tensed wire cathode to vibrations, shocks and the like. Owing to the vibrations of a wire cathode the distance from the wire cathode to the first electrode is not constant, as a result of which the electron beams are formed in an insufficiently uniform manner. This adversely affects the operation of the display device.